Fuel supply to service stations takes place upon the arrival of the transporting tanker truck, when each tank of said service stations is opened.
The filling is achieved by removing the filling cap at the feeding nozzle of the fuel tank, which opens toward the surface of the service station and through which a suitable conducting element, such as a hose, is introduced, providing a temporary fluid communication between the reservoir of the tanker truck and the tank of the service station. The removal of the filling cap is achieved by the easy opening of a conventional padlock, which hinders the movement of the cap lock arms and retains the cap against the nozzle of the tank.
Due to the easy access to the inside of the service station tanks, resulting from the precarious closing system thereof, the contents of said reservoirs are liable to composition adulterations, such adulterations being difficult to prove.
One solution for this problem is to provide the tank filling caps with closing and locking systems which are electrically activated at well determined time periods. Nevertheless, said solution cannot be applied to fuel tanks, due to the danger of explosion caused by electrical sparks, which may occur in this type of lock systems.
Moreover, even though the electrically activated systems present the most elaborate closures in the state of the art, they are still easily activated by conventional electric connectors, which leave no trace of having had the tank cap removed at times which are not solely for the purpose of supplying the tank.